Metal oxide sols are useful as metal oxide film-forming materials, as the inorganic component in organic-inorganic hybrid materials, and in other applications. Several methods of preparation are known.
One specific example, described in JP A 10-298769, is a method of preparing a metal oxide precursor sol by hydrolyzing and polymerizing one or more metal compound, which method is characterized by carrying out the addition of water to the metal compound at a temperature of −20° C. or below.
JP A 1-129032 describes a method for preparing an organic solvent-soluble high-molecular-weight ladder-type polytitanoxane by hydrolyzing titanium tetraalkoxide using 1.0 to 1.7 moles of water per mole of the titanium tetraalkoxide at a temperature of 20 to 90° C. The object of this method is to provide a high-molecular-weight ladder-type polytitanoxane which, in spite of being a high-molecular-weight compound, dissolves in organic solvents and forms a dense thin-film.
JP A 2001-342018 describes a method for preparing a metal oxide precursor solution which involves adding an alcohol solution containing 0.1 to 2.0 moles of water to 1 mole of a metallic salt partially hydrolyzed by the addition of water and the application of heat, then heating so as to hydrolyze the metallic salt and form a metal hydroxide, followed by dehydrative condensation then concentration.